Backwards-compatible delivery of digital cinema content with extended dynamic range

ABSTRACT

A digital cinema signal is encoded to produce a resulting coded digital cinema bitstream. Decoding the resulting coded digital cinema bitstream allows backwards-compatible delivery of digital cinema content. A digital image or video signal is preprocessed to produce two normalized digital image or video signals of differing quality levels and forward and inverse mapping parameters, which relate the normalized digital image or video signals. The preprocessing can be used prior to the encoding of a digital cinema signal to enable backwards-compatible delivery of digital cinema content.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 61/576,141, filed on Dec. 15, 2011, herebyincorporated by reference in its entirety. The present application isalso related to PCT Application PCT/US2011/048861, entitled “ExtendingImage Dynamic Range”, filed on Aug. 23, 2011, which is incorporatedherein by reference in its entirety. The present application is alsorelated to PCT Application PCT/US2010/026953 entitled “LayeredCompression of High Dynamic Range, Visual Dynamic Range, and Wide ColorGamut Video,” filed on Mar. 11, 2010, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates to image processing for digital cinema aswell as preprocessing and coding of digital image and/or video content.More particularly, an embodiment of the present invention relates tobackwards-compatible delivery of digital cinema content with extendedrange and related preprocessing and coding methods.

BACKGROUND

As used herein, the term ‘dynamic range’ (DR) may relate to a capabilityof the human visual system (HVS) to perceive a range of intensity (e.g.,luminance, luma) in an image, e.g., from darkest darks to brightestbrights. In this sense, DR relates to a ‘scene-referred’ intensity. DRmay also relate to the ability of a display device to adequately orapproximately render an intensity range of a particular breadth. In thissense, DR relates to a ‘display-referred’ intensity. Unless a particularsense is explicitly specified to have particular significance at anypoint in the description herein, it should be inferred that the term maybe used in either sense, e.g. interchangeably.

As used herein, the term high dynamic range (HDR) relates to a DRbreadth that spans the some 14-15 orders of magnitude of the HVS. Forexample, well adapted humans with essentially normal vision (e.g., inone or more of a statistical, biometric or opthamological sense) have anintensity range that spans about 15 orders of magnitude. Adapted humansmay perceive dim light sources of a few photons. Yet, these same humansmay perceive the near painfully brilliant intensity of the noonday sunin desert, sea or snow (or even glance into the sun, however briefly toprevent damage). This span though is available to ‘adapted’ humans,e.g., those whose HVS has a time period in which to reset and adjust.

In contrast, the DR over which a human may simultaneously perceive anextensive breadth in intensity range may be somewhat truncated, inrelation to HDR. As used herein, the term ‘visual dynamic range’ (VDR)may relate to the DR that is simultaneously perceivable by a HVS. Asused herein, VDR may relate to a DR that spans 5-6 orders of magnitude.Thus while perhaps somewhat narrower in relation to true scene referredHDR, VDR nonetheless represents a wide DR breadth.

Until fairly recently, displays have had a significantly narrower DRthan HDR or VDR. Television (TV) and computer monitor apparatus that usetypical cathode ray tube (CRT), liquid crystal display (LCD) withconstant fluorescent white back lighting or plasma screen technology maybe constrained in their DR rendering capability to approximately threeorders of magnitude. Such conventional displays thus typify a lowdynamic range (LDR) or standard dynamic range (SDR), in relation to VDRand HDR. Digital cinema systems exhibit some of the same limitations asother display devices.

Advances in their underlying technology, however, will allow futuredigital cinema systems to render image and video content withsignificant improvements in various quality characteristics over thesame content, as rendered on today's digital cinema systems. Forexample, future digital cinema systems may be capable of a DR (e.g. VDR)that is higher than the SDR/LDR of conventional digital cinema systemsas well as a larger color gamut than the color gamut of conventionaldigital cinema systems. The challenge is providing digital cinemacontent which may be displayed on conventional SDR, small color gamutsystems at a standard quality level as well as more advanced VDR, largercolor gamut systems at a correspondingly higher quality level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict schematic diagrams of digital cinema decodingarchitectures in accordance with exemplary embodiments of the presentdisclosure.

FIG. 2 is an example of a pre-processing architecture of a digital imageor video prior to coding.

FIG. 3 is an alternative example of a pre-processing architecture of adigital image or video prior to coding.

FIG. 4 depicts a schematic representation of an embodiment of thepreprocessor of FIGS. 2-3 in greater detail.

FIG. 5 depicts a typical non-linearity when clipping occurs at both thelow and high limits of intensity.

DESCRIPTION OF EXAMPLE EMBODIMENTS

In an example embodiment, a method of decoding a coded digital cinemabitstream is provided, the method comprising: providing a coded digitalcinema bitstream; providing mapping parameters; decoding the codeddigital cinema bitstream, the decoding producing a first decoded digitalcinema image or video with a first dynamic range and a first colorgamut; and expanding the first dynamic range and the first color gamutof the first decoded digital cinema image or video by inverse mappingthe first decoded digital cinema image or video with the mappingparameters, thus obtaining a second decoded digital cinema image orvideo with a second dynamic range higher than the first dynamic rangeand a second color gamut larger than the first color gamut.

In an example embodiment, a method of decoding a coded digital cinemabitstream is provided, the method comprising: providing a coded digitalcinema bitstream; providing mapping parameters; decoding the codeddigital cinema bitstream, the decoding producing a first decoded digitalcinema image or video with a first dynamic range and a first colorgamut; and compressing the first dynamic range and the first color gamutof the first decoded digital cinema image or video by forward mappingthe first decoded digital cinema image or video with the mappingparameters, thus obtaining a second decoded digital cinema image orvideo with a second dynamic range lower than the first dynamic range anda second color gamut smaller than the first color gamut.

In an example embodiment, a method of pre-processing a digital image orvideo signal is provided, the method comprising: processing the digitalimage or video signal by performing color grading to produce a firstdigital image or video signal having a first dynamic range and a firstcolor gamut, and a second digital image or video signal having a seconddynamic range and a second color gamut, the second dynamic range beinghigher than the first dynamic range and the second color gamut beinglarger than the first color gamut; producing a first normalized digitalimage or video signal by pre-processing the first digital image or videosignal; producing a second normalized digital image or video signal bypre-processing the second digital image or video signal, wherein thefirst normalized digital image or video signal is obtainable from thesecond normalized digital image or video signal through a forwardmapping and the second normalized digital image or video signal isobtainable from the first normalized digital image or video signalthrough an inverse mapping; and producing forward mapping parameters andinverse mapping parameters.

In an example embodiment, a method of estimating nonlinear forwardmapping parameters for digital image or video signals is presented, themethod comprising: providing a first digital image or video signal;providing a second digital image or video signal; providing a matrix;inverting the matrix and applying the inverted matrix to the firstdigital image or video signal, thus obtaining an intermediate digitalimage or video signal; and producing nonlinear transformation parameterscorresponding to a nonlinear transformation between the second digitalimage or video signal and the intermediate digital image or videosignal.

In an example embodiment, a method of estimating matrix forward mappingparameters for digital image or video signals is presented, the methodcomprising: at the providing a first digital image or video signal;providing a second digital image or video signal; providing a nonlineartransformation; applying the nonlinear transformation to the seconddigital image or video signal, thus obtaining an intermediate digitalimage or video signal; and producing matrix transformation parameterscorresponding to a matrix transformation between the intermediatedigital image or video signal and the first digital image or videosignal.

In an example embodiment, a method of determining forward mappingparameters for digital image or video signals is presented, the methodcomprising: (a) setting an input matrix equal to an identity matrix; (b)providing a first digital image or video signal; (c) providing a seconddigital image or video signal; (d) inverting the input matrix, thusobtaining an inverted matrix and applying the inverted matrix to thefirst digital image or video signal, thus obtaining an intermediatefirst digital image or video signal; (e) producing nonlineartransformation parameters corresponding to a nonlinear transformationbetween the second digital image or video signal and the intermediatefirst digital image or video signal; (f) applying the nonlineartransformation parameters to the second digital image or video signal,thus obtaining an intermediate second digital image or video signal; (g)producing an estimated matrix corresponding to a matrix transformationbetween the intermediate second digital image or video signal and thefirst digital image or video signal; (h) repeating steps (d) through(g), wherein the input matrix of step (d) is set equal to the estimatedmatrix of step (g); and (i) iterating step (h) until a desired result isobtained.

In an example embodiment, a method of determining forward mappingparameters for digital image or video signals is presented, the methodcomprising: (a) setting input nonlinear transformation parameters toidentity; (b) providing a first digital image or video signal; (c)providing a second digital image or video signal; (d) applying the inputnonlinear transformation parameters to the second digital image or videosignal, thus obtaining an intermediate second digital image or videosignal; (e) producing a matrix corresponding to a matrix transformationbetween the intermediate second digital image or video signal and thefirst digital image or video signal; (f) inverting the matrix andapplying the inverted matrix to the first digital image or video signal,thus obtaining an intermediate first digital image or video signal; (g)producing estimated nonlinear transformation parameters corresponding toa nonlinear transformation between the second digital image or videosignal and the intermediate first digital image or video signal; (h)repeating steps (d) through (g), wherein the input nonlineartransformation parameters of step (d) are set equal to the estimatednonlinear transformation parameters of step (g); and (i) iterating step(h) until a desired result is obtained.

In an example embodiment, a system configured to decode a coded digitalcinema bitstream is presented, the system comprising: a decoderconfigured to decode the coded digital cinema bitstream and produce afirst decoded digital cinema image or video; and a mapping applicatorconfigured to expand a first dynamic range and a first color gamut ofthe first decoded digital cinema image or video by inverse mapping thefirst decoded digital cinema image or video with mapping parameters,thus obtaining a second decoded digital cinema image or video with asecond dynamic range higher than the first dynamic range and a secondcolor gamut larger than the first color gamut.

In an example embodiment, a system configured to decode a coded digitalcinema bitstream is provided, the system comprising: a decoderconfigured to decode the coded digital cinema bitstream and produce afirst decoded digital cinema image or video; and a mapping applicatorconfigured to compress a first dynamic range and a first color gamut ofthe first decoded digital cinema image or video by forward mapping thefirst decoded digital cinema image or video with mapping parameters,thus obtaining a second decoded digital cinema image or video with asecond dynamic range lower than the first dynamic range and a secondcolor gamut smaller than the first color gamut.

In an example embodiment, a system configured to pre-process a digitalimage or video signal is provided, the system comprising: a colorgrading module configured to process the digital image or video signalto produce a first digital image or video signal having a first dynamicrange and a first color gamut, and a second digital image or videosignal having a second dynamic range and a second color gamut, thesecond dynamic range being higher than the first dynamic range in thesecond color gamut being larger than the first color gamut; and apreprocessor configured to produce a first normalized digital image orvideo signal by preprocessing the first digital image or video signal;configured to produce a second normalized digital image or video signalby preprocessing the second digital image or video signal, wherein thefirst normalized digital image or video signal is obtainable from thesecond normalized digital image or video signal through a forwardmapping and the second normalized digital image or video signal isobtainable from the first normalized digital image or video signalthrough an inverse mapping; and configured to produce forward mappingparameters and inverse mapping parameters.

As used herein, the term digital cinema refers to the projection of atheatrical motion picture through a digital cinema projection system. Asused herein, the term digital cinema signal refers to a signalrepresenting digital cinema information.

As used herein, the terms digital image or video signal refer to digitalcontent which may be, by way of example and not of limitation, liveaction, rendered CGI (computer-generated imagery), or from any sourcecapable of producing a digital image or video signal.

FIG. 1A depicts a schematic diagram of a digital cinema decodingarchitecture in accordance with an embodiment of the present disclosure.

A coded bitstream (105A) is input to a decoder (110A). In the embodimentof the figure, the bitstream comprises a 12-bit digital cinema signalwith a 4:4:4 color representation. Typical input bit rates are in the125-250 Mbps range. The digital cinema signal has a dynamic range, e.g.a 2000:1 dynamic range, and a color gamut, e.g. a P3 color gamut. Thedecoder (110A) can be any decoder able to operate on a digital cinemasignal, e.g. a JPEG-2000 decoder.

The decoder (110A) outputs a first digital cinema image or video (115A)with the same dynamic range and color gamut of the coded input bitstream(105A).

Inverse mapping is performed on the digital cinema image or video (115A)by a mapping applicator (120A) to expand the dynamic range and colorgamut of the image or video. In accordance with an embodiment of thedisclosure, the inverse of a nonlinear transformation N followed by amatrix transformation M, i.e. (M∘N)⁻¹ (where the ∘ indicates thetransformation on the right is carried out prior to the transformationon the left), is performed. By way of example, the nonlineartransformation N can be a six segment, cubic spline, while matrix M canbe a 3×3 matrix. The nonlinear transformation parameters Nj and matrixparameters Mij are sent to the mapping applicator (120A) as mappingmetadata (125A). In one embodiment, the mapping applicator can beimplemented as a three-dimensional (3-D) lookup table. While 3-D lookuptables in general are known to those skilled in the art, an embodimentaccording to the present disclosure may use the 3-D lookup table toproduce VDR digital cinema video.

The mapping applicator (120A) outputs a second 12-bit, 4:4:4 digitalcinema image or video (130A) with a higher dynamic range and a largercolor gamut than the dynamic range and color gamut of the first digitalcinema image or video (115A). For example, the second digital cinemaimage or video (130A) can have a 10000:1 dynamic range, and a colorgamut larger than P3.

Therefore, the decoding architecture of FIG. 1A provides a dual-layereddigital cinema content. In particular, the output (135A) of the firstlayer provides a 12-bit, 4:4:4 digital cinema signal (115A) with a firstdynamic range and first color gamut, while the output (140A) of thesecond layer provides a 12-bit, 4:4:4 digital cinema signal (130A) witha second dynamic range higher than the first dynamic range and a secondcolor gamut larger than the first color gamut.

The architecture of FIG. 1A thus provides a ‘single inventory’,backwards-compatible, approach for digital cinema content, which can beused both with (a) digital cinema projectors compatible with the firstdynamic range and the first color gamut and (b) digital cinemaprojectors compatible with the second dynamic range and second colorgamut. Output (135A) will be sent to the first type of projectors, whileoutput (140A) will be sent to the second type of projectors.Alternatively, decoder (110A) and mapping applicator (120A) may belocated in a projector (150A) and one of the outputs (135A, 140A) can besent to a screen (160A).

The person skilled in the art will appreciate that the decoding andmapping architecture of FIG. 1A is a residual-free architecture, whereno residual is employed to improve decoding of the digital cinemabitstream (105A).

In one embodiment, the output (135A) represents a conventional/LDR/SDRdigital cinema version, while the output (140A) represents a VDR/HDRdigital cinema version. As mentioned above, use of the LDR/SDR orVDR/HDR version will depend on the kind of projector available totheatres.

FIG. 1B depicts a schematic diagram of a digital cinema decodingarchitecture in accordance with an alternative embodiment of the presentdisclosure. Such architecture is similar to the embodiment of FIG. 1Awith the following differences. Coded bitstream (105B) of FIG. 1B ischaracterized by a higher dynamic range and a larger color gamut thancoded bitstream (105A) of FIG. 1A. First digital cinema video (115B) issent to forward mapping applicator (120B) to produce a second digitalcinema video (130B) with a lower dynamic range and a smaller color gamutthan the first digital cinema video (115B).

In one embodiment, the output (135B) represents a VDR/HDR digital cinemaversion, while the output (140B) represents a conventional/LDR/SDRdigital cinema version. As mentioned above, use of the LDR/SDR orVDR/HDR version will depend on the kind of projector available totheatres.

While the dual-layer architectures of FIGS. 1A and 1B have beendescribed in terms of conventional/SDR layer vs. VDR/HDR layer, theperson skilled in the art will understand that other layered forms anddenominations are also possible, such as base layer vs. enhancementlayer, first enhancement layer vs. second enhancement layer, and so on.

As noted above, FIG. 1A depicts details of a decoding architecture of adigital cinema bitstream. FIG. 2 depicts instead an example of apre-processing architecture of a digital cinema image or video prior tocoding. In a particular embodiment of the present disclosure, thepre-processing architecture of FIG. 2 can be used in combination withthe decoding architecture of FIG. 1A.

As depicted in FIG. 2, a captured digital cinema signal (205) is inputto a color grading module (210), which outputs a first digital cinemasignal (215) with a first dynamic range and color gamut and a seconddigital cinema signal (220) with a second dynamic range higher than thefirst dynamic range and a second color gamut larger than the first colorgamut. By way of example, signal (215) can be an LDR/SDR signal, whilesignal (220) can be a VDR/HDR signal.

The first digital cinema signal (215) and second digital cinema signal(220) are then normalized in a preprocessor (225), thus producing afirst normalized digital cinema signal (230) and a second normalizeddigital cinema signal (235), where the second normalized digital cinemasignal (235) is identical to the second digital cinema signal (220). Theprocessing through the preprocessor (225) allows the first normalizeddigital cinema signal (230) and the second normalized digital cinemasignal (235) to be related by invertible mapping. In other words, oncenormalized, digital cinema signal (230) can be obtained from digitalcinema signal (235) through forward mapping, while digital cinema signal(235) can be obtained from digital cinema signal (230) through inversemapping. Assuming, for example, that the first signal (230) is indicatedby SDR* (where * is to indicate a normalized version of input (215)) andthe second signal (235) is indicated by VDR* (which is usually equal tothe VDR input (220) to numerical precision), the following relationshipholds true: SDR*=(M∘N)VDR*, where M∘N is the forward mapping operatormentioned above. The preprocessor (225) also produces inverse and/orforward mapping parameters (240) and/or (245) to be sent, e.g., asmetadata. Such parameters allow obtaining signal (235) from signal (230)through inverse mapping or signal (230) from signal (235) throughforward mapping. The mapping parameters obtained and the mappingperformed are such that inverse mapping the SDR* signal will exactlyreproduce the VDR signal.

The first normalized digital cinema signal (230) is then encoded in anencoder (250) and sent to a digital cinema system as a coded bitstream(255). Encoder (250) can be, for example, an encoder configured toprocess the first signal (e.g., an SDR* signal (230)) and not the secondsignal (e.g., a VDR* signal (235)). See, for example, encoder 312 inFIG. 9A of the above mentioned PCT Application PCT/US2011/048861,incorporated herein by reference in its entirety. In an alternativeembodiment, the second signal (e.g., a VDR* signal (335)) may be encodedto allow obtaining an SDR* signal from a VDR* signal. This alternativeembodiment is depicted in FIG. 3. Such embodiment can be combined withFIG. 1B in a manner similar to the combination of FIGS. 2 and 1A.

Normalization pre-processing as described in FIGS. 2 and 3 can be usedto prepare image or video data for backwards-compatible delivery indistribution systems such as digital cinema systems. As noted above,compatibility between the first and the second digital signals discussedabove is obtained at the output of the preprocessor (225/325), where anSDR* signal can be obtained from a VDR* signal and vice versa. In otherwords, the embodiments of FIGS. 2-3 allow different realizations(various levels of SDR) of a master image or video (e.g., VDR) to bederived by transforming the master image or video with a transformationthat is invertible.

According to the embodiment described above, one such transformation isthe M∘N transformation. In other words, a non-linear transformation Nfollowed by a linear matrix transformation M are performed. Suchtransformation (where repeated indices imply summation and where thehigher and lower dynamic range indicators are depicted as VDR and SDR byway of example) can be seen as follows:

$\begin{matrix}\begin{matrix}{C_{i}^{VDR} = \text{i-th color component of VDR image}} \\{C_{i}^{SDR} = \text{i-th color component of SDR image}} \\{C_{i}^{SDR} = {{M_{i,j}{N_{j}\left\lbrack C_{j}^{VDR} \right\rbrack}} = {\sum\limits_{j}{M_{i,j}{N_{j}\left\lbrack C_{j}^{VDR} \right\rbrack}}}}}\end{matrix} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

When the N and M transformation are invertible, the VDR image or videocan be recovered from the SDR image or video:

$\begin{matrix}{C_{i}^{VDR} = {{N_{i}^{- 1}\left\lbrack {M_{i,j}^{- 1}C_{j}^{SDR}} \right\rbrack} = {N_{i}^{- 1}\left\lbrack {\sum\limits_{j}{M_{i,j}^{- 1}C_{j}^{SDR}}} \right\rbrack}}} & {{Equation}\mspace{14mu}(2)}\end{matrix}$

In practice, SDR and VDR images or videos are often created in separatecolor grading passes. The SDR version typically satisfies Equation (1)approximately, but not necessarily exactly. The function ofnormalization is to determine a modified version of the SDR, i.e. SDR*.SDR* and the original VDR satisfy Equation (1) exactly and, furthermore,SDR* and SDR are typically indistinguishable visually. SDR and SDR* canbe visually indistinguishable approximately 99% of the time, and incases where there are visible differences, such differences can bevisible only when the sequence is halted at a particular frame.

In an embodiment of the present disclosure, input bitstream (105A) ofFIG. 1A corresponds to the encoded bitstream (255) of FIG. 2, whilemapping metadata (125A) of FIG. 1A correspond to inverse mappingparameters (240) of FIG. 2. Therefore, according to such embodiment, thedecoding architecture of FIG. 1A can be used in conjunction with theencoding architecture of FIG. 2. In particular, assuming that theinverse mapping of FIG. 1A is performed by inverse transformation(M∘N)⁻¹, the mapping of FIG. 2 is performed by transformation M∘N aslater explained in greater detail. Similarly, the encoding architectureof FIG. 3 can be used with alternative decoding architectures based onthat depicted in FIG. 1B. Input bitstream (105B) of FIG. 1B correspondsto the encoded bitstream (355) of FIG. 3, while mapping metadata (125B)of FIG. 1B correspond to forward mapping parameters (345) of FIG. 3.

Reference will now be made to FIG. 4, which depicts a schematicrepresentation of an embodiment of the preprocessor (225/325) of FIGS. 2and 3 in greater detail. First signal (215/315) and second signal(220/320) are sent to a normalization module (410) which determines theforward mapping parameters of nonlinear transformation N_(j)[ ] and theforward mapping parameters M_(ij) of matrix transformation M. An exampleof how these parameters are obtained will be later explained in detail.

Such forward mapping parameters (245/345) are input to a forward mappingmodule (420) together with the second signal (220/320) in order toobtain the first normalized digital cinema signal (230/330) discussedwith reference to FIGS. 2 and 3, e.g. an SDR* signal. Forward mappingparameters (245/345) are also input to an inversion module (430) toobtain inverse mapping parameters (240/340). Such inverse mappingparameters (240/340) are input to an inverse mapping module (440) toobtain the second normalized digital cinema signal (235/335) of FIGS. 2and 3.

The parameters for N and M can be first estimated from the originaldata. By way of example, such parameters can be determined iterativelyusing two routines “EstimateN” and “EstimateM” that estimate N or Mwhile the other is fixed:N=EstimateN[VDR,SDR,M]M=EstimateM[VDR,SDR,N]

As mentioned above, N can be modeled as a piecewise polynomial such as apiece-wise cubic spline with typically 5-6 segments, while M can be a3×3 matrix.

The routine EstimateN[ ] inverts the matrix M and applies that to theSDR image or video. N is then the transformation between VDR andM⁻¹•SDR. Similarly, the routine EstimateM[ ] applies the non-lineartransformation to VDR and then M is the transformation between N[VDR]and SDR. Thus, there are two estimation sequences, depending uponwhether N or M is first estimated:Set M ⁰ =I;(identity)N ⁰=EstimateN[VDR,SDR,M ⁰];M ¹=EstimateM[VDR,SDR,N ⁰];N ¹=EstimateN[VDR,SDR,M ¹];M ²=EstimateM[VDR,SDR,N ¹];. . . iterate until a desired result is obtained, e.g. mathematicalconvergence.  Sequence A:Set N ⁰ =I;(identity)M ⁰=EstimateM[VDR,SDR,N ⁰];N ¹=EstimateN[VDR,SDR,M ⁰];M ¹=EstimateM[VDR,SDR,N ¹];N ²=EstimateN[VDR,SDR,M ¹];. . . iterate until a desired result is obtained, e.g. mathematicalconvergence.  Sequence B:

Other methods for determining N and M can also be used, such as softwareoptimization packages (e.g. MATLAB).

In most cases the parameters for N[ ] and M determined as describedabove are sufficient. In some cases, the non-linearity must be slightlymodified due to the so-called “clipping” in the SDR signal. FIG. 5depicts a typical non-linearity when clipping occurs at both the low andhigh limits of intensity. In order to make N[ ] invertible, the clippingshould be softened. FIG. 5 depicts varying degrees of softening. Thegreater the softening the larger the differences between SDR and SDR*for the clipped pixels, so the desire to maintain visual equivalencebetween SDR and SDR* constrains this softening.

The methods and systems described in the present disclosure may beimplemented in hardware, software, firmware or any combination thereof.Features described as blocks, modules or components may be implementedtogether (e.g., in a logic device such as an integrated logic device) orseparately (e.g., as separate connected logic devices). The softwareportion of the methods of the present disclosure may comprise acomputer-readable medium which comprises instructions that, whenexecuted, perform, at least in part, the described methods. Thecomputer-readable medium may comprise, for example, a random accessmemory (RAM) and/or a read-only memory (ROM). The instructions may beexecuted by a processor (e.g., a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), or a field programmablelogic array (FPGA)).

All patents and publications mentioned in the specification may beindicative of the levels of skill of those skilled in the art to whichthe disclosure pertains. All references cited in this disclosure areincorporated by reference to the same extent as if each reference hadbeen incorporated by reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

The examples set forth above are provided to give those of ordinaryskill in the art a complete disclosure and description of how to makeand use the embodiments of the backwards-compatible delivery of digitalcinema content with extended range and related preprocessing and codingmethods of the disclosure, and are not intended to limit the scope ofwhat the inventors regard as their disclosure. Modifications of theabove-described modes for carrying out the disclosure may be used bypersons of skill in the video art, and are intended to be within thescope of the following claims.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

The invention claimed is:
 1. A method of decoding a coded digital cinemabitstream (255), wherein the coded digital cinema bitstream (255)comprises a coded digital cinema image (105A, 105B) and mapping metadata(125A, 125B), the method comprising: decoding the coded digital cinemabitstream (105A, 105B) with a decoder to generate a first normalizeddigital cinema image (115A, 115) with a first dynamic range and a firstcolor gamut; and applying the mapping metadata to the first normalizeddigital image to generate a second normalized digital cinema image(130A, 130B) with a second dynamic range and a second color gamut,wherein the mapping metadata comprise an invertible mapping between thefirst and second normalized digital images, wherein the invertiblemapping comprises a lossless invertible nonlinear transformation and aninvertible matrix transformation, wherein generating in an encoder thefirst normalized digital image using the second normalized digital imageand the invertible mapping comprises: applying the nonlineartransformation to the second normalized image to generate a first resultand then applying the matrix transformation to the first result togenerate the first normalized digital image, and generating in thedecoder the second normalized digital image using the first normalizeddigital image and the invertible mapping comprises: applying the inversematrix transformation to the first normalized image to generate a secondresult and then applying the inverse of the nonlinear transformation tothe second result to generate the second normalized digital image. 2.The method of claim 1 wherein the first dynamic range is lower than thesecond dynamic range.
 3. The method of claim 1, wherein decoding thecoded digital cinema image (105B) generates the second digital cinemaimage (115B) and the mapping metadata (125B) are applied to the seconddigital cinema image to generate the first digital cinema image (130B).4. The method of claim 1, further comprising generating an outputdigital cinema image with the second dynamic range and the second gamutfrom the second normalized digital cinema image without using anyresidual image data.
 5. The method of claim 1, wherein the nonlineartransformation comprises a six segment, cubic spline.
 6. The method ofclaim 1, wherein the matrix transformation uses a 3×3 matrix.
 7. Themethod of claim 1, wherein the mapping metadata comprise athree-dimensional lookup table.
 8. The method of claim 1, whereingenerating the second normalized digital image comprises computing${C_{i}^{VDR} = {{N_{i}^{- 1}\left\lbrack {M_{i,j}^{- 1}C_{j}^{SDR}} \right\rbrack} = {N_{i}^{- 1}\left\lbrack {\sum\limits_{j}{M_{i,j}^{- 1}C_{j}^{SDR}}} \right\rbrack}}},$wherein C_(i) ^(VDR) denotes the i-th color component of the secondnormalized digital image, C_(i) ^(SDR) denotes the i-th color componentof the first normalized digital image, N_(i) ⁻¹[ ] denotes the inverseof the nonlinear transformation N_(i)[ ], and M⁻¹ denotes the inverse ofthe matrix transformation M.
 9. A method to generate normalized digitalimages (230, 235, 330, 335) and mapping parameters (240, 245, 340, 345),the method comprising: receiving an input image (205); generating (210)using the input image a first digital image (215) having a first dynamicrange and a first color gamut, and a second digital image (220) having asecond dynamic range and a second color gamut, the second dynamic rangebeing higher than the first dynamic range and the second color gamutbeing larger than the first color gamut; producing a first normalizeddigital image (230) by pre-processing the first digital image; producinga second normalized digital image (235) by pre-processing the seconddigital image; and producing mapping parameters (240, 245), wherein themapping parameters comprise an invertible mapping between the first andsecond normalized digital images, wherein the invertible mappingcomprises an invertible nonlinear transformation and a losslessinvertible matrix transformation, wherein generating the firstnormalized digital image using the second normalized digital image andthe invertible mapping comprises: applying the nonlinear transformationto the second normalized image to generate a first result and thenapplying the matrix transformation to the first result to generate thefirst normalized digital image, and generating the second normalizeddigital image using the first normalized digital image and theinvertible mapping comprises: applying the inverse matrix transformationto the first normalized image to generate a second result and thenapplying the inverse of the nonlinear transformation to the secondresult to generate the second normalized digital image.
 10. The methodof claim 9, wherein generating the second normalized digital image usingthe first normalized digital image comprises computing${C_{i}^{VDR} = {{N_{i}^{- 1}\left\lbrack {M_{i,j}^{- 1}C_{j}^{SDR}} \right\rbrack} = {N_{i}^{- 1}\left\lbrack {\sum\limits_{j}{M_{i,j}^{- 1}C_{j}^{SDR}}} \right\rbrack}}},$wherein C_(i) ^(VDR) denotes the i-th color component of the secondnormalized digital image, C_(i) ^(SDR) denotes the i-th color componentof the first normalized digital image, N_(i) ⁻¹[ ] denotes the inverseof the nonlinear transformation N_(i)[ ], and M⁻¹ denotes the inverse ofthe matrix transformation M.
 11. The method of claim 1, whereingenerating the first normalized digital image using the secondnormalized digital image comprises computing$C_{i}^{SDR} = {{M_{i,j}{N_{i}\left\lbrack C_{j}^{VDR} \right\rbrack}} = {\sum\limits_{i}{M_{i,j}{{N_{i}\left\lbrack C_{j}^{VDR} \right\rbrack}.}}}}$12. The method of claim 9 wherein the first dynamic range is lower thanthe second dynamic range.
 13. The method of claim 9 wherein the secondnormalized digital image (235) is visually identical to the seconddigital image (220).
 14. The method of claim 9, wherein the producing ofthe first normalized digital image (230) comprises: performing anormalization of the first digital image and the second digital image todetermine forward mapping parameters (245); and performing forwardmapping by applying the forward mapping parameters (245) to the seconddigital image (220) to produce the first normalized digital image (230).15. The method of claim 14, wherein the producing of the secondnormalized digital image (235) comprises: inverting the forward mappingparameters (245) to obtain the inverse mapping parameters (240); andperforming inverse mapping by applying the inverse mapping parameters(240) to the first normalized digital image (230) to produce the secondnormalized digital image (235).
 16. The method of claim 14, wherein thedetermining of the forward mapping parameters (245) comprises: (a)setting an input matrix equal to an identity matrix; (b) inverting theinput matrix to obtain an inverted matrix and applying the invertedmatrix to the first digital image (215), thus obtaining an intermediatefirst digital image; (c) producing forward mapping parameters bydetermining nonlinear transformation parameters corresponding to anonlinear transformation between the second digital image (220) and theintermediate first digital image; (d) applying the nonlineartransformation parameters to the second digital image (220), thusobtaining an intermediate second digital image; (e) producing anestimated matrix corresponding to a matrix transformation between theintermediate second digital image and the first digital image (215); (f)repeating steps (b) through (e), wherein the input matrix of step (b) isset equal to the estimated matrix of step (e); and (g) iterating step(f) until a desired result is obtained.
 17. The method of claim 14,wherein the determining of the forward mapping parameters (245)comprises: (a) setting input nonlinear transformation parameters toidentity; (b) applying the input nonlinear transformation parameters tothe second digital image (220) to obtain an intermediate second digitalimage; (c) producing a matrix corresponding to a matrix transformationbetween the intermediate second digital image and the first digitalimage (215); (d) inverting the matrix and applying the inverted matrixto the first digital image (215), thus obtaining an intermediate firstdigital image; (e) producing forward mapping parameters (245) bydetermining estimated nonlinear transformation parameters correspondingto a nonlinear transformation between the second digital image (220) andthe intermediate first digital image; (f) repeating steps (b) through(e), wherein the input nonlinear transformation parameters of step (b)are set equal to the estimated nonlinear transformation parameters ofstep (e); and (g) iterating step (f) until a desired result is obtained.18. The method of claim 9 further comprising: encoding the firstnormalized digital image (230) to generate a first coded digital cinemaimage (255); and combining the first coded digital image and the mappingparameters to generate a coded digital cinema bit stream.
 19. The methodof claim 9, further comprising: encoding the second normalized digitalimage (335) to generate a second coded digital cinema image (355); andcombining the second coded digital image and the mapping parameters togenerate a coded digital cinema bit stream.